1. Field of the Invention
The invention concerns a gas cooled alternating current machine having a stator central part and two stator end parts and, with a fan at each rotor end, the stator sheet metal pack which forms the central part and is clamped between two end plates being subdivided by radially extending cooling ducts into individual partial packs, the cooling ducts being formed by distance protrusions or pins which are fastened to one partial pack end sheet on one duct side, and the stator sheet metal pack being surrounded by a casing.
2. Description of the Prior Art
An electrical machine of the above described generic type is known, for example, from the book by Wiedemann/Kellenberger "Konstruktion elektrischer Maschinen", Springer-Verlag, Berlin, Heidelberg, New York, 1967, page 548, FIG. 473b.
The cooling gas conveyed by the fans flows, on the one hand, through the winding head area and cools the winding heads and, on the other hand, is conducted through axial and radial cooling ducts of the rotor body and through radial cooling ducts of the stator body and also cools the rotor and stator bodies. After the cooling gas emerges from the radial cooling ducts of the stator body and after the passage of the cooling gas from the winding head area through the stator sheet metal body press plates, it arrives in the cooling gas outlet flow area in the central part of the electrical machine. The cooling gas outlet flow area is located between the stator back and the machine casing. Cooling gas escapes from there into the open air or is led to a cooling installation outside the machine for recooling the heated cooling gas.
In the case of an electrical machine whose cooling gas outlet flow areas are, for design reasons, subdivided by the stator sheet metal pack into individual sections, separated from one another in the peripheral direction over the complete axial length, i.e. where there is no annular space between the sheet metal pack and the machine casing, the cooling gas removal system described is only possible under conditions of increased difficulty. This applies both to direct cooling gas removal into the open air from each section of the outlet flow area and to a system connecting the individual sections to one another, with central removal of the cooling gas. In the first case, heated cooling gas would escape at several points from the machine, which, on the one hand, would pollute the environment and make recooling of the warmed cooling gas impossible and, in the second case, additional components, particularly pipework and connecting parts, would be necessary, which additional components have to be attached to the outside of the machine casing. This would, however, produce additional flow paths for the cooling gas and these additional flow paths moreover can not be integrated directly into the stator body. In addition, protective coverings would have to be provided for this externally located connecting pipework and a larger space requirement would be needed for the central part of the electrical machine.